As electronics are becoming smaller in size and higher in performance in recent years, magnet members are also required to be smaller in size and higher in performance, and at the same time, it is required that its cost is lowered. Therefore, when a magnet member obtained by compression molding and sintering magnet member powder is worked such as to adapt the magnet member for a predetermined use, it is required to lower the costs by enhancing the efficiency and to improve the working precision.
FIG. 1a shows a magnet member which is obtained by compression molding and sintering magnet material powder and which has a arc cross section. This magnet member is grounded such that the cross section is shaped like an arc as shown in FIG. 1b and then, it is thinly sliced into a voice coil motor magnet.
Conventionally, when a magnet member 1 of this type is ground, an apparatus shown in FIG. 2 has been used.
In FIG. 2, the reference number 3 represents a turning table, a plurality of magnet members 1 to be worked are fixed on the turning table 3, and the turning table 3 is rotated in the direction of the arrow. A grindstone 5 as a grinding means is disposed such that a flat bottom surface which is a grinding surface is in parallel to a surface of the turning table 3, and the grindstone 5 rotates in the direction of the arrow by a motor 4. The grindstone 5 is rotated, and an upper convex surface of the magnet member 1 having the arc cross section is uniformly ground by a so-called vertical axis plan grinding in which a bottom surface of the grindstone 5 is brought into contact with the upper surface of the magnet member 1 on the turn table 3 so that the magnet member 1 is formed with a flat reference surface 2 as shown in FIG. 3 which is reference for subsequent working.
Thereafter, as shown in FIGS. 4a and 4b, the magnet member 1 is transferred between a pair of guide frames 7 disposed on a table 8 in parallel to each other such that the reference surface 2 is directed downward, and the during the transfer, the upper surface, i.e., a recessed surface is ground into a predetermined shape by the grindstone 6, and the ground recessed surface is subjected to finishing polish.
Further, as shown in FIG. 5, the recessed surface of the magnet member 1 which was subjected to the finishing polish is directed downward, and the magnet member 1 is transferred between a pair of guide frames 10 disposed on a table 9 in parallel to each other, the convex surface of the magnet member 1, i.e., the surface on which the reference surface 2 was formed is ground into a predetermined shape.
Similarly, both sides of the magnet member 1 are ground to obtain a member which is to be cut into the voice coil motor magnet.
As described above, according to the conventional working apparatus, the convex surface of the magnet member is directed upward for grinding the convex surface to form the reference surface and then, the reference surface is directed downward to grind the recessed surface. Therefore, whenever the magnet member to be ground is worked, the upper and lower surfaces of the magnet member must be changed, and it is difficult to work a plurality of surfaces by continuous process. Therefore, the working process is complicated, and the production efficiency is low.
Further, in the conventional working apparatus, grinding liquid used for grinding is injected with respect to a member to be ground which is a working object so as to prevent seizing of the product.
However, it is difficult to constantly maintain the amount of grinding liquid supplied to a portion of the member to be ground. If the amount of the grinding liquid is too much, the member is ground insufficiently, and if the amount of the grinding liquid is too small, since the grinding surface of the grindstone is heated to high temperature, there is inconvenience that diamond comes out from the grindstone or the grindstone is seized.
On the other hand, when members to be ground such as rare-earth sintered magnets for example are contacted with each other and continuously transferred, especially when the members have high brittleness, there is a problem that a crack is generated due to the contact between the members.
It is an object of the present invention to solve the above-described problems, and to provide a working apparatus and a working method of a magnet member capable of continuously and effectively working a large number of magnet members into desired shape.
Especially, it is an object of the invention to provide a working apparatus and a working method of a magnet member capable of further enhancing the productivity by continuously grinding or finishing by grinding upper and lower surfaces of a magnet member.
Further, it is an object of the invention to provide a working apparatus and a working method of a magnet member which suppresses chips or cracks from being generated.
Furthermore, it is an object of the invention to provide a working apparatus and a working method of a magnet member capable of further enhancing the productivity by supplying grinding liquid more reliably and stably.
Furthermore, it is an object of the invention to provide a working apparatus and a working method of a magnet member in which grinding means is not seized or deformed easily by enhancing the permeability of grinding liquid, enhancing the cooling effect, and preventing the temperature rise of a grinding section.